Quiz 11: The Thyroid Gland

Question 1

Thyroid hormones are derived from the amino acid:

(a) Phenylalanine
(b) Methionine
(c) Tyrosine
(d) Histidine

Answer 1

(c) Tyrosine

Question 2

Which statement regarding thyroid hormones is true?

(a) Circulating levels of T3 and T4 are about equal
(b) T3 is more active than T4
(c) The rate of formation of Monoiodotyrosine and diiodotyrosine is about equal
(d) Most of the T3 present in plasma is from its direct release from thyroid storage site

Answer 2

(b) T3 is more active than T4

Question 3

Which of the following statements regarding thyroid hormones is true?

(a) Both protein-bound and free triiodothyronine (T3) and thyroxine (T4) are physiologically active
(b) Total T3 and T4 are influenced by the level of thyroxing-binding globulin
(c) Variation in thyroxine-binding protein levels affects both free T3 and free T4
(d) An elevated serum TSH is diagnostic of hyperthyroidism

Answer 3

(b) Total T3 and T4 are influenced by the level of thyroxing-binding globulin

Question 4

Select the first screening test to do for thyroid disease

(a) Free T4 index
(b) Free T3
(c) Free T4
(d) TSH assay

Answer 4

(d) TSH assay

Question 5

The serum TSH level is almost absent in:

(a) Primary hyperthyroidism
(b) Primary hypothyroidism
(c) Secondary hyperthyroidism
(d) Euthyroid sick syndrome

Answer 5

(a) Primary hyperthyroidism

Question 6

Which of the following statements is true regarding reverse T3 (rT3)?

(a) Formed in blood by degradation of T4
(b) Physiologically active, but less than T3
(c) Decreased in euthyroid sick syndrome
(d) Interferes with the measurement of serum T3

Answer 6

(a) Formed in blood by degradation of T4

Question 7

A patient has an elevated serum-free T3 and free T4 and undetectable TSH. What is the most likely cause of these results?

(a) Primary hyperthyroidism
(b) Secondary hyperthyroidism
(c) Euthyroid with increased TBG
(d) Euthyroid sick syndrome

Answer 7

(a) Primary hyperthyroidism

Question 8

Secretion of hormones by the anterior pituitary may be controlled by the circulating levels of hormones from the respective target gland, as well as hormones secreted by what organ?

(a) Posterior lobe of the pituitary gland
(b) Intermediate lob of the pituitary gland
(c) Hypothalamus
(d) Adrenal medulla

Answer 8

(c) Hypothalamus

Question 9

What is the predominant form of thyroid hormone in the circulation?

(a) Thyroxine
(b) Triiodothyronine
(c) Diiodotyrosine
(d) Monoiodotyrosine

Answer 9

(a) Thyroxine

Question 10

Once synthesized, the thyroid hormones are stored as a component of thyroglobulin in what area of the thyroid gland?

(a) Epithelial cell wall of the follicle
(b) Colloid in the follicle
(c) Isthmus of the thyroid gland
(d) Extracellular space of the thyroid gland

Answer 10

(b) Colloid in the follicle

Question 11

In a patient with suspected primary hyperthyroidism associated with Graves disease, one would expect the following laboratory serum results: free thyroxine ___ and thyroid-stimulating hormone (TSH) ___.

(a) Increased; increased
(b) Increased; decreased
(c) Decreased; increased
(d) Decreased; decreased

Answer 11

(b) Increased; decreased

Question 12

In a patient suspected of having primary myxedema, one would expect the following serum results: free thyroxine (FT4) ___ and thyroid-stimulating hormone (TSH) ___.

(a) Decreased; decreased
(b) Increased; decreased
(c) Decreased; increased
(d) Increased; increased

Answer 12

(c) Decreased; increased

Question 13

Measurement of thyroglobulin can be useful in which of the following disorders?

(a) Hasimoto thyroiditis
(b) Multinodular goiter
(c) Hyperthyroidism
(d) Thyroid adenoma/thyroid cancer

Answer 13

(d) Thyroid adenoma/thyroid cancer

Question 14

What is the major carrier protein of the thyroid hormones in the blood?

(a) Albumin
(b) Thyroxine-binding globulin
(c) Thyroxine-binding prealbumin
(d) Thyroglobulin

Answer 14

(b) Thyroxine-binding globulin

Question 15

The thyroid gland produces all of the following EXCEPT

a) TSH (thyroid stimulating hormone
(b) Thyroglobulin
(c) T3
(d) T4

Answer 15

(a) TSH (thyroid stimulating hormone)

Question 16

The fetus

(a) Does not develop a thyroid gland until the third trimester
(b) Is dependent on thyroid hormone for normal neurologic development
(c) Is not susceptible to damage from radioactive iodine therapy given to the mother
(d) Tested for thyroxine at one year of age in developed countries

Answer 16

(b) Is dependent on thyroid hormone for normal neurologic development

Question 17

Of the following, which will MOST likely interfere with quantitation of thyroglobulin

(a) Antithyroglobulin autoantibodies
(b) Thyroid-stimulating antibodies
(c) TSH receptor antibodies
(d) Thyroid peroxidase antibodies

Answer 17

(a) Antithyroglobulin autoantibodies

Question 18

What is the most common type of laboratory assay that is widely used to assess thyroid hormone concentrations?

(a) Estimation from using a formula
(b) Immunoassay
(c) Potentiometry
(d) Ultrafiltration

Answer 18

(b) Immunoassay

Question 19

What causes primary hypothyroidism?

(a) Absence or dysfunction of the thyroid gland
(b) A hypothalamus disorder
(c) A pituitary disorder
(d) Increased TSH

Answer 19

(a) Absence or dysfunction of the thyroid gland

Question 20

Which of the following sets of results is consistent with primary hypothyroidism (e.g. Hashimoto thyroiditis)

(a) TSH decreased, free T4 decreased, Thyroid peroxidase antibodies (antimicrosomal ab) positive
(b) TSH increased, free T4 increased, Thyroid peroxidase antibodies (antimicrosomal ab) positive
(c) TSH normal, free T4 decreased, Thyroid peroxidase antibodies (antimicrosomal ab) negative
(d) TSH increased, free T4 decreased, Thyroid peroxidase antibodies (antimicrosomal ab) positive

Answer 20

(d) TSH increased, free T4 decreased, Thyroid peroxidase antibodies (antimicrosomal ab) positive